Intravscular filter retrieval device and method

ABSTRACT

A thrombus filter configured for placement in within a blood vessel lumen defined by a blood vessel wall. Methods and devices for selectively removing the thrombus filter when the presence of a filter in the vascular system is no longer desired. The thrombus filter includes a first strand formation, a second strand formation, and a joined portion.

FIELD OF THE INVENTION

[0001] The present invention relates generally to filters for use insideblood vessels. More particularly, the present invention relates tothrombus filters which can be securely adjoined at a selected locationin the vascular system and selectively removed when the presence of afilter in the vascular system is no longer desired.

BACKGROUND OF THE INVENTION

[0002] There are a number of situations in the practice of medicine whenit becomes desirable for a physician to place a filter in the vascularsystem of a patient. One of the most common applications for vascularfilters is the treatment of Deep Venous Thrombosis (DVT). Deep VenousThrombosis patients experience clotting of blood in the large veins ofthe lower portions of the body. These patients are constantly at risk ofa clot breaking free and traveling via the inferior vena cava to theheart and lungs. This process is known as pulmonary embolization.Pulmonary embolization can frequently be fatal, for example when a largeblood clot interferes with the life-sustaining pumping action of theheart. If a blood clot passes through the heart it will be pumped intothe lungs and may cause a blockage in the pulmonary arteries. A blockageof this type in the lungs will interfere with the oxygenation of theblood causing shock or death.

[0003] Pulmonary embolization may be successfully prevented by theappropriate placement of a thrombus filter in the vascular system of apatient's body. Placement of the filter may be accomplished byperforming a laparotomy with the patient under general anesthesia.However, intravenous insertion is often the preferred method of placinga thrombus filter in a patient's vascular system.

[0004] Intravenous insertion of a thrombus filter is less invasive andit requires only a local anesthetic. In this procedure, the thrombusfilter is collapsed within a delivery catheter. The delivery catheter isintroduced into the patients vascular system at a point which isconvenient to the physician. The delivery catheter is then fed furtherinto the vascular system until it reaches a desirable location forfilter placement. The thrombus filter is then released into the bloodvessel from the delivery catheter.

[0005] In the treatment of Deep Venous Thrombosis, a thrombus filter isplaced in the inferior vena cava of a patient. The inferior vena cava isa large vessel which returns blood to the heart from the lower part ofthe body. The inferior vena cava may be accessed through the patient'sfemoral vein.

[0006] Thrombus filters may be placed in other locations when treatingother conditions. For example, if blood clots are expected to approachthe heart and lungs from the upper portion of the body, a thrombusfilter may be positioned in the superior vena cava. The superior venacava is a large vessel which returns blood to the heart from the upperpart of the body. The superior vena cava may by accessed through thejugular vein, located in the patient's neck.

[0007] Once placed inside a blood vessel, a thrombus filter acts tocatch and hold blood clots. The flow of blood around the captured clotsallows the body's lysing process to dissolve the clots.

SUMMARY OF THE INVENTION

[0008] The present invention pertains to thrombus filters which may besecurely adjoined at a selected location in the vascular system andselectively removed when the presence of a filter in the vasculaturesystems is no longer required. The present invention also pertains todevices and method for removing a thrombus filter using minimallyinvasive methods. A thrombus filter in accordance with the presentinvention includes a first strand formation, a second strand formationand a joined portion. The first strand formation and the second strandformation are both comprised of a plurality of strands, each strandhaving a joined end and a free end. The joined ends of the strands arejoined together proximate the joined portion of the thrombus filter. Thestrands radiate away from the joined portion of the thrombus filter sothat the first strand formation and the second strand formation are bothgenerally conical in shape. The strands of the first strand formationand the strands of the second strand formation radiate in generallyopposing directions.

[0009] When the thrombus filter is disposed in a blood vessel, at leastone of the strand formations acts to trap or capture blood clots. Thegenerally conical shape of the strand formation serves to urge capturedblood clots toward the center of the blood flow. The flow of bloodaround the captured blood clots allows the body's natural lysing processto dissolve the clots.

[0010] The free ends of the strands act as opposing wall contactingmembers and serve to position the thrombus filter in the center of ablood vessel lumen. In a presently preferred embodiment, the strands arebiased to spring outward. The radial force applied to the walls of theblood vessel by the strand formations assists in preventing migration ofthe thrombus filter within the blood vessel lumen. The generally opposedorientation of the first strand formation relative to the second strandformation also makes migration of the filter less likely. Migration ofthe thrombus filter within a blood vessel lumen may also be made lesslikely by the inclusion of an anchor member proximate the free end ofeach strand.

[0011] In a presently preferred embodiment, a sliding member is disposedabout the joined portion of the thrombus filter. One or the other of thestrand formations may be collapsed by urging the sliding member towardthe free ends of the strands. Urging the sliding member toward the freeends of strands collapses the strand formation from a generally conicalshape to a generally cylindrical shape. Once the strand formation iscollapsed, it may be urged into the lumen of a retrieval catheter.

[0012] With one strand formation in the lumen of the retrieval catheter,the entire thrombus filter may be urged into the lumen of the retrievalcatheter. Pulling the thrombus filter in the lumen of the retrievalcatheter causes the strands of the second strand formation to collapsefrom a generally conical shape to a generally cylindrical shape. Withall strands in a collapsed position, the thrombus filter may be pulledcompletely into the lumen of the retrieval catheter. With the thrombusfilter disposed inside the lumen of the retrieval catheter, removing thethrombus filter from the body of the patient may be accomplished bywithdrawing the retrieval catheter from the blood vessel lumen.

[0013] In one embodiment of a retrieval catheter, the retrieval catheterincludes an outer tubular member, an inner tubular member and a pullingmeans. One embodiment of the pulling means includes a plurality ofretrieval struts each having a distal end. An engaging member isdisposed proximate the distal end of each strut. In one embodiment, eachengaging member includes a sharp projection. The distal ends of thestruts may be selectively urged inward so that the sharp projectionspenetrate the sliding member of the thrombus filter. Having thus coupledthe struts to the sliding member, a pulling force may be applied to thesliding member by pulling on the proximal ends of the struts.

[0014] In an additional embodiment of a retrieval catheter, the pullingmeans may include flanges fixed to the distal end of each strut. Theflanges are adapted to be disposed about the fixed portion of thethrombus filter. In a presently preferred embodiment, the joined portionof the thrombus filter has a generally cylindrical outer surface. Also,in a presently preferred embodiment, each flange includes an innerradius which is substantially equal to the outer radius of the joinedportion of the thrombus filter. The flanges may be selectively closedaround the joined portion of the thrombus filter. When the flanges areclosed around the joined portion of the thrombus filter, they buttagainst each other to form a generally tubular shell around the joinedportion of the thrombus filter.

[0015] The strands of one or the other of the strand formations may beurged into a collapsed position by urging the flanges toward the freeends of the strands. The flanges may be urged toward the free ends ofthe strands by pulling on the proximal ends of the struts. Once thestrands have been moved into a collapsed position, the strand formationof the thrombus filter may be positioned within the lumen of a retrievalcatheter. This may be accomplished percutaneously by pulling on theproximal end of the struts.

[0016] With one of the strand formations positioned within the lumen ofthe retrieval catheter, the remainder of the thrombus filter may also beurged into the lumen of the retrieval catheter. As described previously,the strands of the second strand formation radiate away from the joinedportion of the thrombus filter in a generally opposed direction relativeto the strands of the first strand formation. The orientation of thestrands allows them to be pulled out of the walls of the blood vesselwith minimal force. The strands of the second strand formation may becollapsed by simultaneously pushing on the proximal end of the retrievalcatheter and pulling on the proximal ends of the struts.

[0017] Pulling the thrombus filter into the lumen of the retrievalcatheter causes the strands of the second formation to collapse from agenerally conical shape to a generally cylindrical shape. With all ofthe strands in a collapsed position, the thrombus filter may be pulledcompletely into the lumen of the retrieval catheter. With the thrombusfilter disposed inside the lumen of the retrieval catheter, removing thethrombus filter from the body of the patient may be accomplished bywithdrawing the retrieval catheter from the blood vessel lumen.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a plan view of a thrombus filter positioned in the lumenof a blood vessel lumen;

[0019]FIG. 2 is a plan view of a removal catheter disposed in a bloodvessel lumen proximate the thrombus filter of FIG. 1;

[0020]FIG. 3 is a plan view of an alternate embodiment of a thrombusfilter and a removal catheter positioned in the lumen of a blood vessellumen;

[0021]FIG. 4 is a plan view of the thrombus filter of FIG. 3illustrating an alternate method of removal; and

[0022]FIG. 5 is a plan view of an alternate embodiment of a thrombusfilter and removal catheter.

DETAILED DESCRIPTION OF THE INVENTION

[0023] The following detailed description should be read with referenceto the drawings, in which like elements in different drawings arenumbered identically. The drawings which are not necessarily to scale,depict selected embodiments and are not intended to limit the scope ofthe invention.

[0024] Examples of constructions, materials, dimensions, andmanufacturing processes are provided for selected elements. All otherelements employ that which is known to those of skill in the field ofthe invention. Those skilled in the art will recognize that many of theexamples provided have suitable alternatives which may be utilized.

[0025] Reference is now made to the drawings, in which like numbersrefer to like elements throughout. FIG. 1 is a plan view of a thrombusfilter 20 positioned in a lumen 22 of a blood vessel 24. Blood vessel 24includes walls 26 which define lumen 22. The main components of thrombusfilter 20 are a first strand formation 30, second strand formation 40,and a joined portion 50.

[0026] First strand formation 30 and second strand formation 40 are bothcomprised of a plurality of strands 32 and 42 respectively. Each strand32 of first strand formation 30 has a joined end 34 and a free end 36.Likewise, each strand 42 of second strand formation 40 has a joined end44 and a free end 46. Joined ends 34 of strands 32 and joined ends 44 ofstrands 42 are joined at joined portion 50 of thrombus filter 20.

[0027] Strands 32 radiate away from joined portion 50 of thrombus filter20 so that first strand formation 30 is generally conical in shape.Likewise, strands 42 radiate away from joined portion 50 of the thrombusfilter 20 such that second strand formation 40 is generally conical inshape. As shown in FIG. 1, strands 32 of first strand formation 30 andstrands 42 of second strand formation 40 radiate in generally opposingdirections.

[0028] When thrombus filter 20 is disposed in a blood vessel, at leastone of the strand formations acts to trap, or capture blood clots. Thegenerally conical shape the strand formation serves to urge capturedblood clots toward the center of the blood flow. The flow of bloodaround the captured blood clots allows the body's natural lysing processto dissolve the clots.

[0029] Strands 32 and 42 act as opposing wall contacting members andserve to position thrombus filter 20 in the center of lumen 22 of bloodvessel 24. In a presently preferred embodiment, strands 32 and 42 arebiased to spring outward. The radial force applied to the walls of theblood vessel by first strand formation 30 and second strand formation 40assists in preventing migration of thrombus filter 20 within bloodvessel lumen 22. The generally opposed orientation of strands 42relative to strands 32 also makes migration of the filter less likely.

[0030] Migration of filter 20 within blood vessel lumen 22 may also madeless likely by the inclusion of anchors on thrombus filter 20. An anchor62 is disposed at free end 46 of each strand 42. Likewise, each free end36 of each strand 32 includes an anchor 60. In FIG. 1, anchors 60 and 62are pictured as sharp projections or barbs. It should be understood thatanchors 60 and 62 may be comprised of other means for anchoring withoutdeparting from the spirit or scope of this invention. It should also beunderstood that embodiments of thrombus filter 20 which include noanchors are possible without departing from the spirit or scope of thepresent invention.

[0031] In the embodiment of FIG. 1, joined portion 50 includes a collar52 disposed about joined ends 34 of strands 32 and joined ends 44 ofstrands 42. A sliding member 70 is disposed about joined portion 50. Inthe embodiment of FIG. 2 sliding member 70 is preferably comprised of aplastic material. Examples of suitable plastic materials includepolyethylene (PE), polypropylene (PP), thermoset polyurethane,thermoplastic polyurethane, and polyether block amide (PEBA). Those withskill in the art will appreciate that sliding member 70 may be comprisedof other materials without deviating from the spirit or scope of thepresent invention. A ring 54 is fixed to joined portion 50 proximate oneend of sliding member 70. Ring 54 may act as a stop to limit the travelof sliding member 70.

[0032] Although two strands 32 and two strands 34 are shown in FIG. 1.Any number of strands 32, 34 may be used. In a presently preferredembodiment first strand formation 30 includes between about 3 strands 32and about 6 strands 32. In a presently preferred embodiment secondstrand formation 40 includes between about 3 strands 42 and about 6strands 42.

[0033] In a presently preferred embodiment, stands 32, 42 are generallycircular in cross section, it should be understood that othercross-sectional shapes are possible without deviating from the spirit orscope of the invention. For example, the cross-sectional shape of stands32, 42 may be circular, rectangular, square, triangular, oval, etc.

[0034] In a presently preferred embodiment, strands 32, 42 are comprisedof nickel-titanium alloy. Suitable nickel-titanium alloys arecommercially available from Memry Technologies (Brookfield,Connecticut), TiNi Alloy Company (San Leandro, Calif.), and Shape MemoryApplications (Sunnyvale, Calif.).

[0035] Those with skill in the art will appreciate that strands 32, 42may be comprised of other metallic or non-metallic materials withoutdeparting from the spirit or scope of the present invention. Examples ofmetallic materials which may be suitable for some applications includestainless steel and titanium. Suitable, non-metallic materials may beselected from the following list, which is not exhaustive:poly(L-lactide) (PLLA), poly(D,L-lactide) (PLA), polyglycolide (PGA),poly(L-lactide-co-D,L-lactide) (PLLA/PLA), poly(L-lactide-co-glycolide)(PLLA/PGA), poly(D, L-lactide-co-glycolide) (PLA/PGA),poly(glycolide-co-trimethylene carbonate) (PGA/PTMC), polyethylene oxide(PEO), polydioxanone (PDS), polycaprolactone (PCL), polyhydroxylbutyrate(PHBT), poly(phosphazene), polyD,L-lactide-co-caprolactone) (PLA/PCL),poly(glycolide-co-caprolactone) (PGA/PCL), polyanhydrides (PAN),poly(ortho esters), poly(phoshate ester), poly(amino acid), poly(hydroxybutyrate), polyacrylate, polyacrylamid, poly(hydroxyethyl methacrylate),polyurethane, polysiloxane and their copolymers.

[0036]FIG. 2 is a plan view of a removal catheter 90 disposed in bloodvessel lumen 22 proximate thrombus filter 20. Removal catheter 90includes an outer tubular member 100 having a lumen 102, a distal end104, and a proximal end 106 (not shown).

[0037] In the embodiment of FIG. 2, an inner tubular member 200 isdisposed within lumen 102 of outer tubular member 100. Inner tubularmember 200 includes a lumen 202, a distal end 204, and a proximal end206 (not shown). An elongate shaft 210 and a pulling means 300 aredisposed within lumen 202 of inner tubular member 200.

[0038] Pulling means 300 includes a plurality of retrieval struts 302each having a distal end 304, a proximal end 306 (not shown), and adistal portion 308. An engaging member 310 is disposed proximate thedistal end 304 of each strut 302. In the embodiment of FIG. 2, eachengaging member 310 includes a sharp projection 312.

[0039] In the embodiment of FIG. 2, distal portions 308 of retrievalstruts 302 are biased to spring outward. Distal portions 308 ofretrieval struts 302 may be selectively urged inward by urging distalend 204 of inner tubular member 200 toward distal ends 304 of retrievalstruts 302. During a surgical procedure, this may be accomplishedpercutaneously by pushing on proximal end 206 (not shown) of innertubular member 200, and/or pulling on proximal ends 306 (not shown) ofretrieval struts 302.

[0040] A method of removing thrombus filter 20 from blood vessel lumen22 may now be described with reference to FIG. 2. The retrieval processtypically begins by introducing catheter 90 into the patients vascularsystem. The retrieval catheter typically enters the patients vascularsystem at a point which is readily accessible to the physician. Once inthe vascular system, the retrieval catheter is urged forward untildistal end 104 of outer tubular member 100 is proximate thrombus filter20.

[0041] For example, if thrombus filter 20 is located in the inferiorvena cava of a patient's vascular system, removal catheter 90 may enterthe vascular system at the femoral vein. Alternately, if thrombus filter20 is located in the superior vena cava of a patient's vascular system,removal catheter 90 may enter the vascular system at the jugular vein.In either case, the filter removal procedure is minimally invasive, andgenerally does not require general anesthesia.

[0042] Preferably, distal portions 308 of retrieval struts 302 will bein a retracted position while the distal end of retrieval catheter 90 isadvanced through the vasculature. Distal portions 308 may be held in aretracted position by inner tubular member 200. When the distal end ofcatheter 90 is proximate thrombus filter 20 inner tubular member 200 maybe pulled back, allowing distal portions 308 of struts 302 to springoutward. Struts 302 may then be urged forward until distal ends 304 ofstruts 302 are proximate slide 70 of thrombus filter 20.

[0043] Distal portions 308 of struts 302 may then be urged towards slide70 by urging distal end 204 of inner tubular member 200 toward distalends 304 of struts 302. This may be accomplished percutaneously bysimultaneously pushing on distal end 206 of inner tubular member 200 andpulling on distal ends 306 of struts 302. When distal portions 308 ofstruts 302 are closed onto slide 70, sharp projections 312 penetrateinto slide 70.

[0044] A pulling force may then be applied to slide 70. In a presentlypreferred embodiment, this pulling force is created by pulling onproximal ends 306 of struts 302. Also in a presently preferredembodiment, thrombus filter 20 may be held in position by pushing thedistal end of elongate shaft 210 against thrombus filter 20.

[0045] Strands 32 may be urged into a collapsed position by urging slide70 toward free ends 36 of strands 32. Once strands 32 have been moved toa collapsed position, first strand portion 30 of thrombus filter 20 maybe positioned within lumen 102 of outer tubular member 100. This may beaccomplished percutaneously by pushing on proximal end 106 of outertubular member 100 and/or pulling on proximal ends 306 of struts 302.

[0046] Once first strand formation 30 is positioned within lumen 102 ofouter tubular member 100, the remainder of thrombus filter 20 may alsobe urged into lumen 102 of outer tubular member 100. As describedpreviously, strands 42 of second strand formation 40 radiate away fromjoined portion 50 of thrombus filter 20 in a generally opposed directionrelative to strands 32 of first strand formation 30. The orientation ofstrands 42 allows them to be pulled out of walls 26 of blood vessel 22with minimal force. Strands 42 may be converted to a collapsed positionby simultaneously by pushing on proximal end 106 of outer tubular member100 and pulling on proximal ends 306 of struts 302.

[0047] Pulling thrombus filter 20 into lumen 102 of outer tubular member100 causes strands 42 to collapse causing second strand formation 40 totransform from a generally conical shape to a generally cylindricalshape. With strands 32 and strands 42 in a collapsed position, thrombusfilter 20 may be pulled completely into lumen 102 of outer tubularmember 100. With thrombus filter 20 disposed inside lumen 102 of outertubular member 100, removing thrombus filter 20 from the body of thepatient may be accomplished by withdrawing retrieval catheter 90 fromblood vessel lumen 22.

[0048]FIG. 3 is a plan view of an alternate embodiment of thrombusfilter 20 positioned in a lumen 22 of a blood vessel 24. Blood vessel 24includes walls 26 which define lumen 22. The main components of thrombusfilter 20 are a first strand formation 30, second strand formation 40,and a joined portion 50.

[0049] First strand formation 30 and second strand formation 40 are bothcomprised of a plurality of strands 32 and 42 respectively. Each strand32 of first strand formation 30 has a joined end 34 and a free end 36.Likewise, each strand 42 of second strand formation 40 has a joined end44 and a free end 46. Joined ends 34 of strands 32 and joined ends 44 ofstrands 42 are joined at joined portion 50 of thrombus filter 20. In theembodiment of FIG. 3, joined portion 50 includes solder 56. Solder 56 isused to fix joined ends 34 of strands 32 and joined ends 44 of strands42 together. Other methods may be used to fix joined ends 34, 44 ofstrands 32, 42 without departing from the spirit or scope of the presentinvention. For example, brazing, welding, mechanical fasteners, and theuse of adhesives may be suitable for some applications.

[0050] Strands 32 radiate away from joined portion 50 of thrombus filter20 so that first strand formation 30 is generally conical in shape.Likewise, strands 42 radiate away from joined portion 50 of the thrombusfilter 20 such that second strand formation 40 is generally conical inshape. As shown in FIG. 1, strands 32 of first strand formation 30 andstrands 42 of second strand formation 40 radiate in generally opposingdirections.

[0051] When thrombus filter 20 is disposed in a blood vessel, at leastone of the strand formations acts to trap, or capture blood clots. Thegenerally conical shape the strand formation serves to urge capturedblood clots toward the center of the blood flow. The flow of bloodaround the captured blood clots allows the body's natural lysing processto dissolve the clots.

[0052] Strands 32 and 42 act as opposing wall contacting members andserve to position thrombus filter 20 in the center of lumen 22 of bloodvessel 24. In a presently preferred embodiment, strands 32 and 42 arebiased to spring outward. The radial force applied to the walls of theblood vessel by first strand formation 30 and second strand formation 40assists in preventing migration of thrombus filter 20 within bloodvessel lumen 22. The generally opposed orientation of strands 42relative to strands 32 also makes migration of the filter less likely.

[0053] Migration of filter 20 within blood vessel lumen 22 may also madeless likely by the inclusion of anchors on thrombus filter 20. An anchor62 is disposed at free end 46 of each strand 42. Likewise, each free end36 of each strand 32 includes an anchor 60. In FIG. 1, anchors 60 and 62are pictured as sharp projections or barbs. It should be understood thatanchors 60 and 62 may be comprised of other means for anchoring withoutdeparting from the spirit or scope of this invention. It should also beunderstood that embodiments of thrombus filter 20 which include noanchors are possible without departing from the spirit or scope of thepresent invention.

[0054] Two slides 72 and 74 are disposed about joined portion 50. In theembodiment of FIG. 3 each sliding member 70, 74 is comprised of ahelical coil. The strength of slides 72, 74 may be increased bysoldering or otherwise bonding consecutive turns of the helical coil toeach other. In FIG. 3, slide 74 is shown in partial cross section.Slides 72, 74 include coupling members 76, 78 respectively.

[0055] In FIG. 3, a removal catheter 400 is disposed in lumen 22 ofblood vessel 24. Removal catheter 400 includes a lumen 402, a distal end404, and a proximal end 406 (not shown). An elongate member 500 isdisposed in lumen 402 of removal catheter 400. Elongate member 500includes a distal end 504, a proximal end 506 (not shown), and acoupling member 502 disposed proximate distal end 504.

[0056] A method of removing thrombus filter 20 from blood vessel lumen22 may now be described with reference to FIG. 3. The retrieval processtypically begins by introducing the catheter into the patients vascularsystem. The retrieval catheter typically enters the patients vascularsystem at a point which is readily accessible to the physician. Once inthe vascular system, the retrieval catheter is urged forward untildistal end 404 is proximate thrombus filter 20.

[0057] For example, if thrombus filter 20 is located in the inferiorvena cava of a patient's vascular system, removal catheter 400 may enterthe vascular system at the femoral vein. Alternately, if thrombus filter20 is located in the superior vena cava of a patient's vascular system,removal catheter 400 may enter the vascular system at the jugular vein.In either case, the filter removal procedure is minimally invasive, andgenerally does not require general anesthesia.

[0058] The retrieval catheter is advanced through blood vessel lumen 22until distal end 404 catheter 400 is proximate thrombus filter 20.Distal end 504 of elongate member 500 is then coupled to sliding member72. This may be accomplished by mating coupling member 502 of elongatemember 500 with coupling member 76 of the sliding member 72. A pullingforce is then applied to sliding member 72. In a presently preferredembodiment, this pulling force is created by pulling on proximal end 506(not shown) of elongate member 500.

[0059] Pulling on sliding member 72 urges sliding member 72 toward freeends 36 of strands 32. As sliding member 72 moves, it causes strands 32to collapse. Once strands 32 move to a collapsed position, first strandformation 30 of thrombus filter 20 may be urged into lumen 402 ofretrieval catheter 400.

[0060] Once first strand formation 30 has entered lumen 402 of retrievalcatheter 400, thrombus filter 20 may be urged further into lumen 402 ofcatheter 400. As described previously, strands 42 of second strandformation 40 radiate away from joined portion 50 of thrombus filter 20in a generally opposed direction relative to strands 32 of first strandformation 30. The orientation of strands 42 allows them to be pulledaway from walls 26 of blood vessel 24 with minimal force.

[0061] Pulling thrombus filter 20 into lumen 402 of retrieval catheter400 causes strands 42 to collapse causing second strand formation 40 totransform from a generally conical shape to a generally cylindricalshape. The collapse of strands 32 and 42 allows all of thrombus filter20 to be disposed in lumen 402 of catheter 400. With thrombus filter 20disposed inside lumen 402 of retrieval catheter 400, removing thrombusfilter 20 from the body of the patient may be accomplished bywithdrawing retrieval catheter 400 from blood vessel lumen 22.

[0062] An additional method of removing thrombus filter 20 from bloodvessel lumen 22 has been envisioned in which two removal catheters 400Aand 400B are utilized. This method may be described with reference toFIG. 4.

[0063] The retrieval process typically begins by introducing catheters400A, 400B into the patients vascular system. Once in the vascularsystem, retrieval catheters 400A, 400B are urged forward until distalends 404A, 404B are proximate thrombus filter 20.

[0064] Retrieval catheters 400A, 400B enter the patient's vascularsystem at points which allow them to approach thrombus filter 20 fromsubstantially opposing directions. For example, removal catheter 400Amay enter the vascular system at the femoral vein and removal catheter400B may enter the vascular system at the patients right internaljugular vein.

[0065] Retrieval catheter 400A is advanced through the vasculature ofthe patient until distal end 404A of catheter 400A is proximate firststrand formation 30 of thrombus filter 20. Likewise, retrieval catheter400B is advanced through the vasculature of the patient until distal end404A of catheter 400B is proximate second strand formation 40 ofthrombus filter 20.

[0066] Distal end 504A of elongate member 500A is then coupled tosliding member 72. This may be accomplished by mating coupling member502A of elongate member 500A with coupling member 76 of the slidingmember 72. Likewise, distal end 504B of elongate member 500B is coupledto sliding member 74. This may be accomplished by mating coupling member502B of elongate member 500B with coupling member 78 of the slidingmember 74.

[0067] Sliding member 72 may now be urged towards distal ends 36 ofstrands 32 by applying a pulling force to proximal end 506A (not shown)of elongate member 500A. Simultaneously, sliding member 74 may now beurged towards distal ends 46 of strands 42 by applying a pulling forceto proximal end 506B (not shown) of elongate member 500B.

[0068] Urging sliding member 72 toward free ends 36 of strands 32 causesfirst strand formation 30 to collapse. Likewise, urging sliding member74 toward free ends 46 of strands 42 causes second strand formation 40to collapse.

[0069] Once strands 32, 42 move to a collapsed position, thrombus filter20 may be urged into lumen 402A of retrieval catheter 400A. Alternately,thrombus filter 20 may be pulled into lumen 402B of retrieval catheter400B. With thrombus filter 20 disposed inside the lumen of a ofretrieval catheter, removing thrombus filter 20 from the body of thepatient may be accomplished by withdrawing the retrieval catheter fromblood vessel lumen 22.

[0070] Other embodiments have been envisioned. For example, slidingmember 72 and sliding member 74 may be replaced with one sliding membercomprised of a continuous helical coil. In this embodiment, pulling inopposing directions on coupling members 76, 78 would cause the helicalcoil to expand in length.

[0071]FIG. 5 is a plan view of an alternate embodiment of thrombusfilter 20 positioned in a lumen 22 of a blood vessel 24. Blood vessel 24includes walls 26 which define lumen 22. The main components of thrombusfilter 20 are a first strand formation 30, second strand formation 40,and a joined portion 50.

[0072] First strand formation 30 and second strand formation 40 are bothcomprised of a plurality of strands 32 and 42 respectively. Each strand32 of first strand formation 30 has a joined end 34 and a free end 36.Likewise, each strand 42 of second strand formation 40 has a joined end44 and a free end 46. Joined ends 34 of strands 32 and joined ends 44 ofstrands 42 are joined at joined portion 50 of thrombus filter 20. In theembodiment of FIG. 5, joined portion 50 includes a collar 52 disposedabout joined ends 34, 44 of strands 32, 42.

[0073] Strands 32 radiate away from joined portion 50 of thrombus filter20 so that first strand formation 30 is generally conical in shape.Likewise, strands 42 radiate away from joined portion 50 of the thrombusfilter 20 such that second strand formation 40 is generally conical inshape. As shown in FIG. 5, strands 32 of first strand formation 30 andstrands 42 of second strand formation 40 radiate in generally opposingdirections.

[0074] When thrombus filter 20 is disposed in blood vessel lumen 22, atleast one of the strand formations acts to trap, or capture blood clots.The generally conical shape the strand formation serves to urge capturedblood clots toward the center of the blood flow. The flow of bloodaround the captured blood clots allows the body's natural lysing processto dissolve the clots.

[0075] Strands 32 and 42 act as opposing wall contacting members andserve to position thrombus filter 20 in the center of lumen 22 of bloodvessel 24. In a presently preferred embodiment, strands 32 and 42 arebiased to spring outward. The radial force applied to the walls of theblood vessel by first strand formation 30 and second strand formation 40assists in preventing migration of thrombus filter 20 within bloodvessel lumen 22. The generally opposed orientation of strands 42relative to strands 32 also makes migration of the filter less likely.

[0076] Migration of filter 20 within blood vessel lumen 22 may also madeless likely by the inclusion of anchors on thrombus filter 20. An anchor62 is disposed at free end 46 of each strand 42. Likewise, each free end36 of each strand 32 includes an anchor 60. In FIG. 5, anchors 60 and 62are pictured as sharp projections or barbs. It should be understood thatanchors 60 and 62 may be comprised of other means for anchoring withoutdeparting from the spirit or scope of this invention. It should also beunderstood that embodiments of thrombus filter 20 which include noanchors are possible without departing from the spirit or scope of thepresent invention.

[0077]FIG. 5 includes a removal catheter 590 disposed in blood vessellumen 22 proximate thrombus filter 20. Removal catheter 590 includes anouter tubular member 600 having a lumen 602, a distal end 604, and aproximal end 606 (not shown).

[0078] In the embodiment of FIG. 5, an inner tubular member 700 isdisposed within lumen 602 of outer tubular member 600. Inner tubularmember 700 includes a lumen 702, a distal end 704, and a proximal end706 (not shown). An elongate shaft 710 and a pulling means 800 aredisposed within lumen 702 of inner tubular member 700.

[0079] Pulling means 800 includes a plurality of struts 802 each havinga distal end 804, a proximal end 806 (not shown), and a distal portion808. An engaging member 810 is disposed proximate the distal end 804 ofeach strut 802. In the embodiment of FIG. 5, each engaging member 810includes a flange 812. Flanges 812 are adapted to be disposed aboutcollar 52 of thrombus filter 20. In a presently preferred embodiment,collar 52 has a generally cylindrical outer surface. Also in a presentlypreferred embodiment each flange 812 includes an inner radius which issubstantially equal to the outer radius of collar 52. When flanges 812are closed around collar 52 they butt against each other to form agenerally tubular shell around collar 52.

[0080] In the embodiment of FIG. 5, distal portions 808 of retrievalstruts 802 are biased to spring outward. Distal portions 808 ofretrieval struts 802 may be selectively urged inward by urging distalend 704 of inner tubular member 700 toward distal ends 804 of retrievalstruts 802. During a surgical procedure, this may be accomplishedpercutaneously by pushing on proximal end 706 (not shown) of innertubular member 700, and/or pulling on proximal ends 806 (not shown) ofretrieval struts 802.

[0081] A method of removing thrombus filter 20 from blood vessel lumen22 may now be described with reference to FIG. 5. The retrieval processtypically begins by introducing catheter 590 into the patients vascularsystem. Once in the vascular system, the retrieval catheter is urgedforward until distal end 604 of outer tubular member 600 is proximatethrombus filter 20.

[0082] Preferably, distal portions 808 of retrieval struts 802 will bein a retracted position while the distal end of retrieval catheter 590is advanced through the vasculature. Distal portions 808 may be held ina retracted position by inner tubular member 700.

[0083] When the distal end of catheter 590 is proximate thrombus filter20 inner tubular member 700 may be pulled back, allowing distal portions808 of struts 802 to spring outward. Struts 802 may then be urgedforward until distal ends 804 of struts 802 are proximate joined portion50 of thrombus filter 20.

[0084] Distal portions 808 of struts 802 may then be urged towardsjoined portion 50 by urging distal end 604 of inner tubular member 700toward distal ends 804 of struts 802. This may be accomplishedpercutaneously by simultaneously pushing on distal end 706 (not shown)of inner tubular member 700 and pulling on distal ends 806 of struts802. When distal portions 808 of struts 802 are closed onto joinedportion 50, flanges 812 close around collar 52. Flanges 812 are adaptedso that they butt together and form a substantially tubular shell aroundcollar 52.

[0085] Strands 32 may be urged into a collapsed position by urgingflanges 812 toward free ends 36 of strands 32. Flanges 812 may be urgedtoward free ends 36 of strands 32 by pulling on proximal ends 806 ofstruts 802. In a presently preferred method, thrombus filter 20 may beheld in position by pushing the distal end of elongate shaft 710 againstthrombus filter 20. Once strands 32 have been moved to a collapsedposition, first strand portion 30 of thrombus filter 20 may bepositioned within lumen 602 of outer tubular member 600. This may beaccomplished percutaneously by pushing on proximal end 606 of outertubular member 600 and/or pulling on proximal ends 806 of struts 802.

[0086] Once first strand formation 30 is positioned within lumen 602 ofouter tubular member 600, the remainder of thrombus filter 20 may alsobe urged into lumen 602 of outer tubular member 600. As describedpreviously, strands 42 of second strand formation 40 radiate away fromjoined portion 50 of thrombus filter 20 in a generally opposed directionrelative to strands 32 of first strand formation 30. The orientation ofstrands 42 allows them to be pulled out of walls 26 of blood vessel 22with minimal force. Strands 42 may be converted to a collapsed positionby simultaneously by pushing on proximal end 606 of outer tubular member600 and pulling on proximal ends 806 of struts 802.

[0087] Pulling thrombus filter 20 into lumen 602 of outer tubular member600 causes strands 42 to collapse causing second strand formation 40 totransform from a generally conical shape to a generally cylindricalshape. With strands 32 and strands 42 in a collapsed position, thrombusfilter 20 may be pulled completely into lumen 602 of outer tubularmember 600. With thrombus filter 20 disposed inside lumen 602 of outertubular member 600, removing thrombus filter 20 from the body of thepatient may be accomplished by withdrawing retrieval catheter 590 fromblood vessel lumen 22.

[0088] Numerous advantages of the invention covered by this documenthave been set forth in the foregoing description. It will be understood,however, that this disclosure is, in many respects, only illustrative.Changes may be made in details, particularly in matters of shape, size,and arrangement of parts without exceeding the scope of the invention.The inventions's scope is, of course, defined in the language in whichthe appended claims are expressed.

What is claimed is:
 1. A thrombus filter element for placement within ablood vessel lumen defined by a blood vessel wall comprising: aplurality of strands each having a joined portion and a free end; thejoined portion of each strand being fixed to a joined portion of thethrombus filter; and a sliding member disposed about the joined portionof the thrombus filter.
 2. The thrombus filter of claim 1 , furtherincluding a coupling member fixed to the sliding member.
 3. The thrombusfilter of claim 2 , wherein the coupling member is a loop.
 4. Thethrombus filter of claim 2 , wherein the coupling member is a hook. 5.The thrombus filter of claim 2 , wherein the coupling member is ashoulder.
 6. The thrombus filter of claim 1 , wherein the sliding memberis comprised of a plastic material.
 7. The thrombus filter of claim 6 ,wherein the plastic material is polyethylene.
 8. The thrombus filter ofclaim 6 , wherein the plastic material is polypropylene.
 9. The thrombusfilter of claim 6 , wherein the plastic material is polyether blockamide.
 10. The thrombus filter of claim 1 , wherein the strands arecomprised of nickel titanium alloy.
 11. The thrombus filter of claim 1 ,wherein the joined portion of the thrombus filter includes a collar. 12.A thrombus filter element for placement within a blood vessel lumendefined by a blood vessel wall comprising: a plurality of strands havinga first grouping and a second grouping, wherein the first grouping andthe second grouping radiate in opposing directions from a joined portionof the thrombus filter, each strand having a free end and a joinedportion; the joined portion of each strand being fixed to a joinedportion of the thrombus filter; and a sliding member disposed about thejoined portion of the thrombus filter.
 13. The thrombus filter of claim12 , further including a coupling member fixed to the sliding member.14. The thrombus filter of claim 13 , wherein the coupling member is aloop.
 15. The thrombus filter of claim 13 , wherein the coupling memberis a hook.
 16. The thrombus filter of claim 13 , wherein the couplingmember is a shoulder.
 17. The thrombus filter of claim 12 , wherein thesliding member is comprised of a plastic material.
 18. The thrombusfilter of claim 17 , wherein the plastic material is polyethylene. 19.The thrombus filter of claim 17 , wherein the plastic material ispolypropylene.
 20. The thrombus filter of claim 17 , wherein the plasticmaterial is polyether block amide.
 21. The thrombus filter of claim 12 ,wherein the strands are comprised of nickel titanium alloy.
 22. Thethrombus filter of claim 12 , wherein the joined portion of the thrombusfilter includes a collar.
 23. A method of selectively removing athrombus filter from a blood vessel lumen comprising the steps of:providing a thrombus filter disposed in a blood vessel lumen; thethrombus filter having a plurality of strands having a first groupingand a second grouping, wherein the first grouping and the secondgrouping radiate in generally opposing directions, each strand having afree end and a joined portion; the joined portion of each strand beingfixed to a joined portion of the thrombus filter; and a sliding memberdisposed about the joined portions of the strands; providing a retrievalcatheter having a distal end, a proximal end, and a lumen extendingtherebetween; providing a means for pulling disposed proximate thedistal end of the retrieval catheter; advancing the retrieval catheterthrough the blood vessel lumen until the distal end of the catheter isproximate the thrombus filter; joining the means for pulling to thesliding member of the thrombus filter; urging the sliding member towardthe free ends of the first grouping of the strands; urging the thrombusfilter inside the lumen of the retrieval catheter; and withdrawing theretrieval catheter from the blood vessel lumen.
 24. A method ofselectively removing a thrombus filter from a blood vessel lumencomprising the steps of: providing a thrombus filter disposed in a bloodvessel lumen; the thrombus filter having a plurality of strands having afirst grouping and a second grouping, wherein the first grouping and thesecond grouping radiate in generally opposing directions, each strandhaving a free end and a joined portion; the joined portion of eachstrand being fixed to a joined portion of the thrombus filter; providinga retrieval catheter having a distal end, a proximal end, and a lumenextending therebetween; providing a plurality of struts, each struthaving a proximal end, a distal end; providing a plurality of flanges,each flange fixed to the distal end of one of the plurality of struts;advancing the retrieval catheter through the blood vessel lumen untilthe distal end of the catheter is proximate the thrombus filter;advancing the struts longitudinally through the blood vessel until theflanges are disposed proximate the joined portions of the strands of thethrombus filter; closing the flanges around the joined portion of thethrombus filter; urging the flanges toward the free ends of the firstgrouping of the strands; urging the thrombus filter inside the lumen ofthe retrieval catheter; and withdrawing the retrieval catheter from theblood vessel lumen.